Packet Tracer/Spanning Tree Issue

MonkerzMonkerz Member Posts: 842
Ok, I had some spare time at work today and decided to mess around with packet tracer a little bit. I ran into a problem, if you look at the screen shot you will see a redundant switched network at the lower right hand side. There is a constant broadcast storm once spanning-tree begins forwarding ports.

Spanning tree seems confused as to which switch is suppose to be the root for vlans 1-3. Now I know what you are thinking, but yes I did (or attempted to) manually set the root bridge. CA_SW1 has its priority set to 0 for vlans 1-100.

What I think the problem is, it seems like every one of these switches have the exact same MAC addy. I assigned different priorities to each switch, incrementing up from 0 to 4096 to 8192...etc, thinking that would fix something....nada.

Any ideas? I have hosted the packet tracer from my skydrive if you want to play with it.

http://cid-8177b48068b05452.office.live.com/self.aspx/.Public/Messing^_Around.pkt

Comments

  • PristonPriston Member Posts: 999 ■■■■□□□□□□
    You have 2 switchs with the same hostname
    display name CA_ACC_SW2 is hostname CA_ACC_SW1
    A.A.S. in Networking Technologies
    A+, Network+, CCNA
  • alan2308alan2308 Member Posts: 1,854 ■■■■■■■■□□
    Priston wrote: »
    You have 2 switchs with the same hostname
    display name CA_ACC_SW2 is hostname CA_ACC_SW1

    That shouldn't matter, when you first turn everything on, every switch has a hostname of Switch.


    For some reason, on VLAN 2, VLAN2_ACC3 and VLAN2_ACC4 have both ports forwarding. Every other switch looks ok here. I'm not seeing the issue with every switch having the same MAC address, and CA_SW1 does appear to be the root bridge for all VLAN's. My initial thought is a PT bug as I don't see anything in your configs that would cause that. But I don't have 11 physical switches to duplicate your topology. :)

    I'm using PT 5.3.1 FWIW.
  • MonkerzMonkerz Member Posts: 842
    alan2308 wrote: »
    That shouldn't matter, when you first turn everything on, every switch has a hostname of Switch.


    For some reason, on VLAN 2, VLAN2_ACC3 and VLAN2_ACC4 have both ports forwarding. Every other switch looks ok here. I'm not seeing the issue with every switch having the same MAC address, and CA_SW1 does appear to be the root bridge for all VLAN's. My initial thought is a PT bug as I don't see anything in your configs that would cause that. But I don't have 11 physical switches to duplicate your topology. :)

    I'm using PT 5.3.1 FWIW.

    Maybe just a bug with my version. I am using v5.1. This is what I see for CA_SW1:
    CA_SW1#sh span
    VLAN0001
    Spanning tree enabled protocol rstp
    Root ID Priority 1
    Address 0030.A3BA.9B12
    This bridge is the root
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

    Bridge ID Priority 1 (priority 0 sys-id-ext 1)
    Address 0030.A3BA.9B12
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
    Aging Time 20

    Interface Role Sts Cost Prio.Nbr Type
    ---- ---


    Fa0/1 Desg FWD 19 128.1 P2p
    Fa0/2 Desg FWD 19 128.2 P2p
    Gi1/1 Desg FWD 19 128.25 P2p

    VLAN0002
    Spanning tree enabled protocol rstp
    Root ID Priority 1
    Address 0030.A3BA.9B12
    Cost 19
    Port 1(FastEthernet0/1)
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

    Bridge ID Priority 2 (priority 0 sys-id-ext 2)
    Address 0030.A3BA.9B12
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
    Aging Time 20

    Interface Role Sts Cost Prio.Nbr Type
    ---- ---


    Fa0/1 Altn FWD 19 128.1 P2p
    Fa0/2 Desg FWD 19 128.2 P2p
    Gi1/1 Desg FWD 19 128.25 P2p

    VLAN0003
    Spanning tree enabled protocol rstp
    Root ID Priority 1
    Address 0030.A3BA.9B12
    Cost 19
    Port 1(FastEthernet0/1)
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

    Bridge ID Priority 3 (priority 0 sys-id-ext 3)
    Address 0030.A3BA.9B12
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
    Aging Time 20

    Interface Role Sts Cost Prio.Nbr Type
    ---- ---


    Fa0/1 Desg FWD 19 128.1 P2p
    Fa0/2 Altn BLK 19 128.2 P2p
    Gi1/1 Desg FWD 19 128.25 P2p

    When I try to trace down the root for VLAN2 and VLAN3, it sends me in a circle;
    CA_SW1 -> CA_ACC_SW1 -> VLAN2_ACC1 -> CA_ACC_SW2 -> VLAN2_ACC1
  • MonkerzMonkerz Member Posts: 842
    Ok, just downloaded PT v 5.3 and now CA_SW1 is showing as root for all VLANs, but VLAN2_ACC2, VLAN2_ACC3 and VLAN2_ACC4 has both ports forwarding like you saw.
  • mikej412mikej412 Member Posts: 10,086 ■■■■■■■■■■
    Take any unexpected result in a simulator with a grain of salt.

    I put it in simulation mode and watched about 5 seconds worth of all packets and 10 seconds worth of STP packets and didn't see a loop.

    With simulators save your network, close and reopen. Repeat until you get the desired/expected result -- or give up or try it on real hardware.
    :mike: Cisco Certifications -- Collect the Entire Set!
  • mikej412mikej412 Member Posts: 10,086 ■■■■■■■■■■
    Monkerz wrote: »
    Ok, just downloaded PT v 5.3 and now CA_SW1 is showing as root for all VLANs, but VLAN2_ACC2, VLAN2_ACC3 and VLAN2_ACC4 has both ports forwarding like you saw.
    I'm using 5.3 -- CA_SW1 is root for all VLANs.

    I only see VLAN2_ACC3 with both ports forwarding, VLAN2_ACC4 only has the 1 port forwarding.

    If there are multiple 5.3 builds, I'm probably on an earlier build -- which would mean they are adding software bugs instead of removing software bugs. icon_lol.gif
    :mike: Cisco Certifications -- Collect the Entire Set!
  • gregorio323gregorio323 Member Posts: 201 ■■■□□□□□□□
    usually packet tracer is bugged when it comes to STP you have to save and restart.
  • MonkerzMonkerz Member Posts: 842
    mikej412 wrote: »

    With simulators save your network, close and reopen. Repeat until you get the desired/expected result -- or give up or try it on real hardware.

    This is really just for fun or the sake of doing it. Unfortunately, my wallet is not as large as my imagination, so I have to resort to simulator/emulators. Of course I do have a few switches and routers to play with, but while on a conference call or upgrade bridge boredom sets in and I can't really walk into our noisy data center to tinker with my lab.

    I do have GNS3, which works great for routing emulation, but unless I am mistaken it does not really support switching.

    If anyone has any ideas or good emulation software (free or $$), I'd like to give it a try.
  • alan2308alan2308 Member Posts: 1,854 ■■■■■■■■□□
    Monkerz wrote: »
    This is really just for fun or the sake of doing it. Unfortunately, my wallet is not as large as my imagination, so I have to resort to simulator/emulators. Of course I do have a few switches and routers to play with, but while on a conference call or upgrade bridge boredom sets in and I can't really walk into our noisy data center to tinker with my lab.

    I do have GNS3, which works great for routing emulation, but unless I am mistaken it does not really support switching.

    If anyone has any ideas or good emulation software (free or $$), I'd like to give it a try.

    You can slap a NM16esw into a router and do quite a bit of switching. And here is a list of what it can't do.

    Free CCNA Workbook is able to cover nearly all of the CCNA topics with GNS3, so it's more capable than you might think.
  • MonkerzMonkerz Member Posts: 842
    Well then, I retract my previous statement.
  • mikej412mikej412 Member Posts: 10,086 ■■■■■■■■■■
    Monkerz wrote: »
    If anyone has any ideas or good emulation software (free or $$), I'd like to give it a try.
    Dynamips (with the Dynagen or GNS3 front ends) is about as good as you're going to get. At least there you're dealing with the actual Switch Module limitations (and hardware simulation in Dynamips).

    Boson has been around for a while -- so if they didn't add to many bugs for version 8.x of their simulator it may work better for switching than Packet Tracer.

    Someday Packet Tracer may become a full CCNA network simulation solution -- but it's still not there. And it still has bugs.

    There's also Mimic. I think they've added an online option -- but I'm not sure if you're just stuck with their canned network(s) or if you can build your own. I tried their recent demo (and the iPhone app) but their web site was having issues and I haven't been back to try again. In the past it was outrageously expensive -- but the online access price seems more reasonable now (if it works).

    You can get the "Cisco Press Simulator" -- which seem to just be flash based exercises to run through. It's not a build your own network and go wild type thing like Dynamips/Boson/Packet Tracer.
    :mike: Cisco Certifications -- Collect the Entire Set!
  • MonkerzMonkerz Member Posts: 842
  • alan2308alan2308 Member Posts: 1,854 ■■■■■■■■□□
    I immediately thought of this thread when I came across this blog post tonight. A Spanning Tree/PVST LAB in GNS3.

    The Net: Spanning tree, PVST lab - GNS3
Sign In or Register to comment.